Apr 2, 2015

Utah, Michigan studying high-density tart cherry options

It’s too early to tell if high-density growing systems are viable for tart cherries, but the earlier production, higher yields, improved fruit quality, more efficient pesticide applications and other advantages they’ve brought to apples and sweet cherries make them worth a serious study.

Brent Black, an Extension fruit specialist at Utah State University, has been studying high-density growing systems for tart cherries for the last few years. He shared some preliminary research results with growers in Michigan earlier this year, during the 2015 Northwest Michigan Orchard & Vineyard Show.

Black said there isn’t enough data yet to tell tart cherry growers it’s definitely time to move to high-density systems, but he and other researchers are trying to work out a scheme that’s economically viable.

Tart cherries are an important crop in Utah – the No. 2 producer, after Michigan –making up nearly half the state’s total fruit acreage. But like the rest of the industry, Utah’s tart growers are more or less using the same-sized trees and the same harvesting techniques that were in use 50 years ago, Black said.

Meanwhile, many apple and sweet cherry growers have moved to high-density systems – smaller, more uniform trees spaced closer together – which have several advantages. In apples, high-density trees can start producing within a few years, while it can take the typical tart cherry tree up to a dozen years to reach peak production. There’s also an increase in sugar, color, firmness and other fruit quality traits. For tart cherries – most of which are a single variety, Montmorency, and destined for processing markets – fruit quality isn’t a major consideration right now, though higher-quality cherries could change that, Black said.

Mechanization is another potential advantage. Smaller, more uniform trees could more easily fit an over-the-row harvester – like the kind used to harvest berries. High-density trees also make for more efficient pesticide applications. Another potentially huge benefit is dry matter content, which is higher in high-density apples. Since many tart cherries are dried, a higher percentage of dry matter could increase their market value, he said.

To study these and other potential benefits for tart cherries, Black and his research team planted high-density test blocks in 2010. They ran into various challenges over the next few years – including poor tree vigor, hail and difficulties acquiring a harvesting machine – which contributed to inconsistent yields. They still need to figure out the best rootstocks for Utah’s alkaline soils, optimum tree and row spacings, the best pruning and thinning strategies, the long-term productivity of the trees – and so on. The research is far from complete, he said.

Michigan

Black is working with researchers in Michigan, who also are studying high-density systems for tart cherries.

With help from block grant funding, Michigan State University (MSU) researchers will plant four high-density tart cherry orchards in 2017: three at grower sites in northwest Michigan and one in southwest Michigan. They’ll use two rootstocks developed by MSU cherry breeder Amy Iezzoni, Clinton and Cass, as well as Gisela 3 and 5. They’re developing tree spacings and other details with Black’s Utah team, according to Nikki Rothwell, coordinator of MSU’s Northwest Michigan Horticulture Research Center.

“We have decent data from a rootstock trial we set up here at the station, and growers can see that we are getting earlier and higher yields,” Rothwell said. “I think growers are getting more excited than they were even a year ago.”

– Matt Milkovich